The present invention relates to the steering axle of a vehicle, such as a scooter, with two tilting front wheels.
In order to increase the steering comfort and road handling of scooters, the front axle of certain models was improved by incorporating two sideways tilting steering wheels. This type of vehicle is described for instance in WO 9721583 or in the patent application EP 1180476 A1.
This patent application relates to a vehicle 10 shown schematically in FIG. 1. The vehicle 10 comprises a chassis 11 supporting an engine 12, a rear wheel 13 connected to the engine 12, and two front wheels 14 and 15 which are part of a suspension system 16 (shown schematically), a handlebar 17 and a steering column 18 with a tubular sleeve 19 secured to the chassis 11. In association with the right and left front wheels 14, 15, the suspension system 16 includes a deformable quadrilateral composed of an upper suspension arm 20D (D for right) or 20G (G for left), respectively, a lateral arm 21, respectively, 21D or 21G, a lower arm 22D or 22G, respectively, and for the two right and left quadrilaterals, the lower extremity 19i of the sleeve 19. The tubular sleeve 19 comprises two supports, an upper support 23 and a lower support 24 welded to the sleeve. The upper arms 20D and 20G are connected on one side by pivots to the upper support 23 and, on the other side, by ball joints 25 and 26, respectively, to the lateral arms 21D and 21G. Similarly the lower arms 22D and 22G are connected on one side by pivots 27 to the lower support 24 and, on the other side, by ball joints 28 and 29, respectively, to the lateral arms. This deformable parallelepiped structure with pivots and ball joints allows for the sideways tilting of the vehicle, while maintaining the front wheels parallel (or at least approximately parallel) to each other. The two upper arms 20D and 20G are interconnected by means of an elastic suspension, comprised of a fluid shock absorber 30 and a spring 31, which allows for the vertical movement of the front part of the vehicle.
Although adequate, the above described architecture is not entirely satisfactory, especially for what concerns the road handling of the scooter.